This invention relates generally to printed circuit (PC) board assembly and is particularly directed to a PC board hold down system and clamp therefor for securely maintaining a circuit board in a flat configuration during the insertion of electronic components thereon.
The generally flat, board-like element upon which an electronic circuit is fabricated in many electronic apparatus is typically referred to as "substrate", or circuit board, and is used primarily for mechanical support and insulating purposes, such as with ceramic, plastic, and glass substrates, but semiconductor and ferrite substrates may also provide useful electrical functions. The conductive elements coupling circuit components are typically in the form of elongated metal foils which may be positioned on one or both sides of the circuit board. Circuit components are frequently positioned on a first side of the circuit board, with their associated electrical leads extending through predrilled apertures in the board so as to contact conductive foils on the reverse side of the board in completing the circuit.
Although initially assembled by hand, today these circuit boards are typically assembled by high speed, automatic positioning and insertion arrangements which sequentially move each circuit board in position in an assembly line fashion for positioning of the various electronic components thereon. Because of the small size of the components in general and the apertures in the circuit board in particular, precise alignment is required between the circuit board and the component insertion apparatus. Misalignment of the component leads with the circuit board apertures typically results in bent electrical leads or misalignment of the leads with respect to the conductors on the circuit board. Bent and misaligned electrical leads result in inadequate or incorrect electrical circuit connections requiring the entire circuit board assembly to be either discarded or repaired prior to installation in the end product.
Misalignment between component leads or terminals and the circuit board apertures is frequently due to the nonflat character of the circuit board. Irregularities in the flatness of the circuit board may arise from various factors such as irregularities in the manufacturing process, excessive heat or moisture in the circuit board storage environment, or mishandling of the circuit boards following their fabrication. Even relatively minor out-of-flatness distortions in the circuit board may result in misalignment between the mounting apertures in the board and the component leads to be inserted therein. Rather than being inserted through a mounting aperture so as to extend to the other side of the circuit board, a component lead may contact the upper surface of the circuit board due to its nonplanar configuration during the insertion procedure so as to prevent proper mounting and electrical connection of the component on the circuit board.
The present invention is intended to overcome the aforementioned limitations of the prior art by providing a hold down system and clamp therefor for securely maintaining a nonplanar circuit board in a flat configuration to insure precise alignment between the circuit board and automatic component handling apparatus during the insertion of components on the board. With an electronic component positioned immediately above the circuit board and in alignment with mounting apertures therein, the component may be lowered onto the circuit board with its lead extending through the mounting apertures to permit proper mounting of the component and its electrical connection to various conductors on either, or both, sides of the circuit board.